Oblicz
a)
(-3)^2-9\frac{9}{10}:(-3^2)=9-\frac{99}{10}:(-9)=9+\frac{99}{10}\cdot \frac{1}{9}=9+\frac{11}{10}=9+1,1=10,1
b)
\frac{9^{17}-9^{19}}{12*9^{17}}=\frac{9^{17}-9^{17}\cdot 9^2}{12\cdot 9^{17}}=\frac{\not9^{17}(1-9^2)}{12\cdot \not9^{17}}=\frac{1-81}{12}=-\frac{80}{12}=-\frac{20}{3}=-6\frac{2}{3}